In a multiprotocol label switching (MPLS) network, a signaling protocol may be used to set up a label switched path (LSP) in the MPLS network. MPLS may permit a network to direct a flow of packets along a predetermined path (e.g., a LSP) across the network. As part of setting up the LSP, label switching routers (LSRs) included in the MPLS network may set up a label information base (LIB) that maps an incoming label from an input port of the LSR to an output port of the LSR. The LSRs may forward packets along links through the MPLS network based on labels attached to the packets that indicate which LSP to use. The label may be swapped to a new label at each node hop. In this way, a LSP may identify the specific path of nodes (e.g., routers) and links that the packets take through the MPLS network. Traffic Engineering (TE) may be implemented in the MPLS network to provide better performance. TE may steer some of the traffic scheduled to follow the original LSP to an alternate path to enable better bandwidth management and utilization between a pair of routers. Thus, a traffic engineering label switched path (TE-LSP) may not be bound to a specific path to a destination node.
Resource reservation protocol (RSVP) for TE-LSPs may be used to communicate control plane reservations across a network. RSVP may be used by either a host or a router to request or deliver specific qualities of services (QoS) for application data streams or flows. RSVP may define how applications place reservations and how they may relinquish the reserved resources once the need for them has ended. In RSVP TE-LSPs, various protection mechanisms can be used to protect against link and node failures. These failure mechanisms may construct a bypass tunnel across a protected link/node. Generally, the bypass tunnel gets used only in case of failure.
In some customer networks, TE-LSPs are used for forwarding mission critical applications. Often TE-LSPs use Layer 2 circuits that are provisioned and sold by third parties and/or that the customer does not control. As a fail-safe mechanism, customers may typically provision two of such LSPs over disjointed paths.